When an encoding or decoding method varies depending on a characteristic of an input signal, a Unified Speech and Audio Codec (USAC) may improve a coding performance. In this instance, in the USAC, a speech coder may perform encoding/decoding with respect to a signal, similar to a speech from among input signals, and an audio coder may perform encoding/decoding with respect to a signal similar to an audio.
A USAC may process an input signal based on mode switching between Linear Prediction Domain (LPD) modes. Also, the USAC may process an input signal based on mode switching between an LPD mode and a Frequency Domain (FD) mode. The USAC may process a signal by applying a window sequence to a frame of an input signal based on mode switching. However, a window sequence processing method that may improve a coding efficiency in comparison with a USAC in a conventional art.